Heterogeneous display elements and methods for their fabrication

Abstract

Optically heterogeneous display elements utilize fused pigment particles, which may be manufactured with polymer shells having desired charge, photoresponse, or density characteristics. The particles may be microencapsulated prior to formation of the display element, so that the element is formed internally within the container in which it is permanently housed. The element may function as a bichromal display, a light valve, or a programmable magnetic element.

What is claimed is:  
     
       1. A method of forming an optically heterogeneous display element, the method comprising the steps of: 
       a. encapsulating a suspension of particles, the suspension comprising a mixture of first particles each having a first physical characteristic and second particles each having a second physical characteristic, the first and second particles having different optical properties, the first and second physical characteristics conferring a differential response to an external stimulus;  
       b. applying the external stimulus to the encapsulated particles to separate the first and second particles; and  
       c. fusing the separated first particles to form a first discrete element and joining the separated second particles to form a second discrete element.  
     
     
       2. The method of claim  1  wherein the first and second discrete elements comprise two substantially hemispherical regions differentially responsive to the external stimulus. 
     
     
       3. The method of claim  1  wherein the first and second discrete elements comprise two substantially hemispherical regions differentially responsive to different external stimuli. 
     
     
       4. The method of claim  1  wherein the fusing step comprises fusing the particles by exposure to energy in the form of at least one of (a) heat, (b) actinic radiation, (c) ultrasound, and (d) RF radiation. 
     
     
       5. The method of claim  1  wherein the first and second particles contrast visually, the element being encapsulated in an optically transmissive container. 
     
     
       6. The method of claim  1  wherein the differential response persists within the single element such that the element may oriented within the capsule by exposure to the external stimulus. 
     
     
       7. The method of claim  6  wherein the external stimulus is an applied electric field, the first and second physical characteristics being different zeta potentials. 
     
     
       8. The method of claim  6  wherein the external stimulus is an applied magnetic field, the first and second physical characteristics being different magnetizations. 
     
     
       9. The method of claim  1  wherein the first and second discrete elements are encapsulated and further comprising the steps of: 
       a. forming a plurality of display elements in accordance with steps (a) through (c);  
       b. disencapsulating the elements; and  
       c. encapsulating multiple ones of the disencapsulated elements in optically transmissive containers as multiple-element displays.  
     
     
       10. The method of claim  1  wherein the first and second discrete elements are hemispherical the elements being unattached to each other. 
     
     
       11. The method of claim  1  wherein the first and second discrete elements are joined into a single spherical element.